The effects of the size and volumetric content of rubber powder on properties of concrete,including flexural strength, compressive strength and permeability, were studied in this paper.Two different particle sizes (20 mesh and 60 mesh) of rubber powder were chosen to replace the sand with volume content of sand as5%, 10%, 15%, 20%, 25%, 30% respectively.The results showed that both flexural and compressive strength of concrete, especially compressive strength, decreased with the increase of rubber content.Moreover, the smaller the particle of rubber powder, the greater the strength of the concrete, which was not obvious as effect of rubber powder content on the strength of concrete.The impermeability of concrete increased with the increase of rubber powder content.The electric flux of concrete with 30% rubber powder reduced to about 900 C, which was only 1/5 of that with 5%.At the same content, smaller rubber particle has positive effects on the impermeability of concrete.